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Frontiers in Immunology 2023
Topics: Humans; COVID-19; Platelet Activation
PubMed: 37818358
DOI: 10.3389/fimmu.2023.1285355 -
Circulation Research Jan 2024
Topics: Mitochondrial Dynamics; Blood Platelets; Megakaryocytes; Hemostasis; Platelet Activation
PubMed: 38236952
DOI: 10.1161/CIRCRESAHA.123.323867 -
Platelets Dec 2023Arterial tonometry and vascular calcification measures are useful in cardiovascular disease (CVD) risk assessment. Prior studies found associations between tonometry...
Arterial tonometry and vascular calcification measures are useful in cardiovascular disease (CVD) risk assessment. Prior studies found associations between tonometry measures, arterial calcium, and CVD risk. Activated platelets release angiopoietin-1 and other factors, which may connect vascular structure and platelet function. We analyzed arterial tonometry, platelet function, aortic, thoracic and coronary calcium, and thoracic and abdominal aorta diameters measured in the Framingham Heart Study Gen3/NOS/OMNI-2 cohorts ( = 3,429, 53.7% women, mean age 54.4 years ±9.3). Platelet reactivity in whole blood or platelet-rich plasma was assessed using 5 assays and 7 agonists. We analyzed linear mixed effects models with platelet reactivity phenotypes as outcomes, adjusting for CVD risk factors and family structure. Higher arterial calcium trended with higher platelet reactivity, whereas larger aortic diameters trended with lower platelet reactivity. Characteristic impedance (Zc) and central pulse pressure positively trended with various platelet traits, while pulse wave velocity and Zc negatively trended with collagen, ADP, and epinephrine traits. All results did not pass a stringent multiple test correction threshold ( < 2.22e-04). The diameter trends were consistent with lower shear environments invoking less platelet reactivity. The vessel calcium trends were consistent with subclinical atherosclerosis and platelet activation being inter-related.
Topics: Female; Male; Humans; Calcium; Pulse Wave Analysis; Blood Pressure; Platelet Activation; Atherosclerosis
PubMed: 37609998
DOI: 10.1080/09537104.2023.2238835 -
Blood Sep 2023von Willebrand factor (VWF) mediates primary hemostasis and thrombosis in response to hydrodynamic forces. We previously showed that high shear promoted self-association...
von Willebrand factor (VWF) mediates primary hemostasis and thrombosis in response to hydrodynamic forces. We previously showed that high shear promoted self-association of VWF into hyperadhesive strands, which can be attenuated by high-density lipoprotein (HDL) and apolipoprotein A-I. In this study, we show that low-density lipoprotein (LDL) binds VWF under shear and enhances self-association. Vortexing VWF in tubes resulted in its loss from the solution and deposition onto tube surfaces, which was prevented by HDL. At a stabilizing HDL concentration of 1.2 mg/mL, increasing concentrations of LDL progressively increased VWF loss, the effect correlating with the LDL-to-HDL ratio and not the absolute concentration of the lipoproteins. Similarly, HDL diminished deposition of VWF in a post-in-channel microfluidic device, whereas LDL increased both the rate and extent of strand deposition, with both purified VWF and plasma. Hypercholesterolemic human plasma also displayed accelerated VWF accumulation in the microfluidic device. The initial rate of accumulation correlated linearly with the LDL-to-HDL ratio. In Adamts13-/- and Adamts13-/-LDLR-/- mice, high LDL levels enhanced VWF and platelet adhesion to the myocardial microvasculature, reducing cardiac perfusion, impairing systolic function, and producing early signs of cardiomyopathy. In wild-type mice, high plasma LDL concentrations also increased the size and persistence of VWF-platelet thrombi in ionophore-treated mesenteric microvessels, exceeding the accumulation seen in similarly treated ADAMTS13-deficient mice that did not receive LDL infusion. We propose that targeting the interaction of VWF with itself and with LDL may improve the course of thrombotic microangiopathies, atherosclerosis, and other disorders with defective microvascular circulation.
Topics: Mice; Humans; Animals; von Willebrand Factor; Lipoproteins, LDL; Thrombosis; Hemostasis; Platelet Adhesiveness; ADAMTS13 Protein
PubMed: 37506337
DOI: 10.1182/blood.2023019749 -
Journal of Thrombosis and Haemostasis :... Jun 2024Platelets are well-known players in several cardiovascular diseases such as atherosclerosis and venous thrombosis. There is increasing evidence demonstrating that... (Review)
Review
Platelets are well-known players in several cardiovascular diseases such as atherosclerosis and venous thrombosis. There is increasing evidence demonstrating that reactive oxygen species (ROS) are generated within activated platelets. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is a major source of ROS generation in platelets. Ligand binding to platelet receptor glycoprotein (GP) VI stimulates intracellular ROS generation consisting of a spleen tyrosine kinase-independent production involving NOX activation and a following spleen tyrosine kinase-dependent generation. In addition to GPVI, stimulation of platelet thrombin receptors (protease-activated receptors [PARs]) can also trigger NOX-derived ROS production. Our recent study found that mitochondria-derived ROS production can be induced by engagement of thrombin receptors but not by GPVI, indicating that mitochondria are another source of PAR-dependent ROS generation apart from NOX. However, mitochondria are not involved in GPVI-dependent ROS generation. Once generated, the intracellular ROS are also involved in modulating platelet function and thrombus formation; therefore, the site-specific targeting of ROS production or clearance of excess ROS within platelets is a potential intervention and treatment option for thrombotic events. In this review, we will summarize the signaling pathways involving regulation of platelet ROS production and their role in platelet function and thrombosis, with a focus on GPVI- and PAR-dependent platelet responses.
Topics: Humans; Blood Platelets; Reactive Oxygen Species; Thrombosis; Oxidation-Reduction; Signal Transduction; Platelet Membrane Glycoproteins; Animals; Platelet Activation; Mitochondria; NADPH Oxidases; Receptors, Thrombin; Receptors, Proteinase-Activated
PubMed: 38460839
DOI: 10.1016/j.jtha.2024.02.018 -
Thrombosis and Haemostasis Dec 2023Cirrhotic patients display an increased risk for both bleeding and thrombosis. We investigated platelet activation across Child-Pugh stages (CPSs) and portal...
BACKGROUND
Cirrhotic patients display an increased risk for both bleeding and thrombosis. We investigated platelet activation across Child-Pugh stages (CPSs) and portal hypertension (PH) severity.
MATERIAL AND METHODS
A total of 110 cirrhotic patients were prospectively included. CPS and hepatic venous pressure gradient (HVPG) were determined. Platelet surface expression of P-selectin and activated glycoprotein (GP) IIb/IIIa were measured by flow cytometry before/after stimulation with protease-activated receptor (PAR)-1 (thrombin receptor activating peptide, TRAP) and PAR-4 (AYPGKF) agonists, epinephrine, and lipopolysaccharide (LPS).
RESULTS
Platelet count was similar across CPS but lower with increasing PH severity. Expression of P-selectin and activated GPIIb/IIIa in response to TRAP and AYPGKF was significantly reduced in platelets of CPS-B/C versus CPS-A patients (all 0.05). Platelet P-selectin expression upon epinephrine and LPS stimulation was reduced in CPS-C patients, while activated GPIIb/IIIa in response to these agonists was lower in CPS-B/C (all 0.05). Regarding PH severity, P-selectin and activated GPIIb/IIIa in response to AYPGKF were lower in HVPG ≥20 mmHg patients (both 0.001 vs. HVPG < 10 mmHg). Similarly, activated GPIIb/IIIa was lower in HVPG ≥20 mmHg patients after TRAP stimulation (0.01 vs. HVPG < 10 mmHg). The lower platelet surface expression of P-selectin and activated GPIIb/IIIa upon stimulation of thrombin receptors (PAR-1/PAR-4) in CPS-B/C and HVPG ≥20 mmHg patients was paralleled by reduced antithrombin-III levels in those patients (all 0.05). Overall, PAR-1- and PAR-4-mediated platelet activation correlated with antithrombin-III levels (0.001).
CONCLUSION
Platelet responsiveness decreases with increasing severity of liver cirrhosis and PH but is potentially counterbalanced by lower antithrombin-III levels.
Topics: Humans; P-Selectin; Prospective Studies; Lipopolysaccharides; Blood Platelets; Platelet Glycoprotein GPIIb-IIIa Complex; Platelet Activation; Receptor, PAR-1; Anticoagulants; Liver Cirrhosis; Hypertension, Portal; Epinephrine; Antithrombins; Platelet Aggregation
PubMed: 37517407
DOI: 10.1055/s-0043-1771187 -
Arteriosclerosis, Thrombosis, and... Oct 2023Heparin-induced thrombocytopenia (HIT) is a major concern for all individuals that undergo cardiac bypass surgeries or require prolonged heparin exposure. HIT is a life-...
BACKGROUND
Heparin-induced thrombocytopenia (HIT) is a major concern for all individuals that undergo cardiac bypass surgeries or require prolonged heparin exposure. HIT is a life- and limb-threatening adverse drug reaction with an immune response following the formation of ultra-large immune complexes that drive platelet activation through the receptor FcγRIIA. Thrombotic events remain high following the standard of care treatment with anticoagulants, while increasing risk of bleeding complications. This study sought to investigate a novel approach to treatment of HIT. Recent reports demonstrate increased procoagulant activity in HIT; however, these reports required analysis ex vivo, and relevance in vivo remains unclear.
METHODS
Using human and mouse model systems, we investigated the cooperativity of PARs (protease-activated receptors) and FcγRIIA in HIT. We challenged humanized FcγRIIA transgenic mice with or without endogenous mouse Par4 (denoted as IIA-Par4 or IIA-Par4, respectively) with a well-established model IgG immune complex (anti [α]-CD9). Furthermore, we assessed the procoagulant phenotype and efficacy to treat HIT utilizing inhibitor of 12-LOX (12[S]-lipoxygenase), VLX-1005, previously reported to decrease platelet activation downstream of FcγRIIA and PAR4, using the triple allele HIT mouse model.
RESULTS
IIA-Par4 mice given αCD9 were severely thrombocytopenic, with extensive platelet-fibrin deposition in the lung. In contrast, IIA-Par4 mice had negligible thrombocytopenia or pulmonary platelet-fibrin thrombi. We observed that pharmacological inhibition of 12-LOX resulted in a significant reduction in both platelet procoagulant phenotype ex vivo, and thrombocytopenia and thrombosis in our humanized mouse model of HIT in vivo.
CONCLUSIONS
These data demonstrate for the first time the need for dual platelet receptor (PAR and FcγRIIA) stimulation for fibrin formation in HIT in vivo. These results extend our understanding of HIT pathophysiology and provide a scientific rationale for targeting the procoagulant phenotype as a possible therapeutic strategy in HIT.
Topics: Humans; Mice; Animals; Thrombocytopenia; Heparin; Blood Platelets; Anticoagulants; Mice, Transgenic; Phenotype; Fibrin; Platelet Factor 4
PubMed: 37345522
DOI: 10.1161/ATVBAHA.123.319434 -
International Journal of Cardiology Nov 2023
Topics: Humans; Platelet Activation; Syndrome; Takotsubo Cardiomyopathy
PubMed: 37586422
DOI: 10.1016/j.ijcard.2023.131256 -
Diagnosis (Berlin, Germany) May 2024
PubMed: 37906210
DOI: 10.1515/dx-2023-0129 -
Research and Practice in Thrombosis and... Oct 2023Flow cytometry is an important technique for understanding multiple aspects of blood platelet biology. Despite the widespread use of the platform for assessing platelet...
BACKGROUND
Flow cytometry is an important technique for understanding multiple aspects of blood platelet biology. Despite the widespread use of the platform for assessing platelet function, the optimization and careful consideration of preanalytical conditions, sample processing techniques, and data analysis strategies should be regularly assessed. When set up and designed with optimal conditions, it can ensure the acquisition of robust and reproducible flow cytometry data. However, these parameters are rarely described despite their importance.
OBJECTIVES
We aimed to characterize the effects of several preanalytical variables on the analysis of blood platelets by multiparameter fluorescent flow cytometry.
METHODS
We assessed anticoagulant choice, sample material, sample processing, and storage times on 4 distinct and commonly used markers of platelet activation, including fibrinogen binding, expression of CD62P and CD42b, and phosphatidylserine exposure.
RESULTS
The use of suboptimal conditions led to increases in basal platelet activity and reduced sensitivities to stimulation; however, the use of optimal conditions protected the platelets from artifactual stimulation and preserved basal activity and sensitivity to activation.
CONCLUSION
The optimal preanalytical conditions identified here for the measurement of platelet phenotype by flow cytometry suggest a framework for future development of multiparameter platelet assays for high-quality data sets and advanced analysis.
PubMed: 37854456
DOI: 10.1016/j.rpth.2023.102205